In a statement issued before the convention John McNesby, president of the Fraternal Order of Police Lodge 5 in Philadelphia, said the union was "shocked, saddened and insulted".

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He said: "We will not soon forget that the Democratic Party and Hillary Clinton are excluding the widows and other family members of police officers killed in the line of duty who were victims of explicit and not implied racism. Mrs Clinton, you should be ashamed of yourself, if that is possible.”

Mr McNesby accused Mrs Clinton of "pandering to the interests of people who do not know all the facts to win an election".

The Clinton campaign responded that two police officers including Charles Ramsey, the former Philadelphia Police Commissioner, were also speaking at the convention.

A spokeswoman said: "As Hillary Clinton has said we need to support heroic police officers who put their lives on the line every day as well as listen to the voices of mothers who have lost their children.

“We look forward to highlighting the courageous efforts of law enforcement with speakers at our convention and praising their work to keep our communities safe."